To be honest,graphics is the less important. Remember Starcraft 1 and Warcraft trilogy? (( 1 ,2 and 3)) ? Well,these games have not so great graphics,but there's loads of people out there playing it,and you wonder ''Why?'',oh well I'll tell you. These games may suck graphicly,but they've indeed HOT stories (( Warcraft does )) and an excellent gameplay.
Lets see it this way: On WoW,you do quests,instances to level. After you reach 70,you start doing harder instances in the objective to achieve better equipments. As you've got them,you join bigger and stronger guilds which focus mainly on end-game raids.You have LOADS of fun raiding. After you've done all the raids and you're geared ((which takes MONTHS AND MONTHS )),you've got the various PvP modes. Battlegrounds (( 4 of them )),Arenas ((2v2,3v3,5v5)),each one of these giving rewards,thing you don't get in here. Also,in WoW,it's not about how you gear yourself (( Can't say build,because you don't do /dex+ 40 /stamina+ 30 in there)) ,but how you play. I've beaten people with the best PvP set ,with myself having PvE gear.
Now on RO: You level,you party to do that,no fun,gets boring.After reaching level 99,you turn level 1 again. You level,and party,even more boring. After getting to 99,all you can do is either farm items/equipments or PvP.
Wonder why Blizzard makes billions and Gravity doesn't make a million? There's your answer. I've played RO for long,and I play WoW,so... correct me if I'm wrong.